EXCELLENT Article Daniel!
That is what were talking about, true Experimentation!
That is incredible research and modification.
Thank You for posting it on the Forum.
This will help many people to have an alternative transceiver to play with eSSB.

We are honored to have you as a Member.
Thank You again for your contribution to this fine facet of Amateur Radio.

This Thread will be Sticky Posted to the top of this Topic.

Take Care,_________________Voodoo Guru
From Deep in the IDD of the Sub-Harmonix Realm

Is anyone out there capable and experienced to do this. My Icom is my only radio so a decent turnaround would be nice. And what would be a price on this job. I'm good at soldering just not good with soldering at the critical scale. I could just send u the Dsp board if that's all that's needed for the modification. Thanks! Very interested in equipping my icon with this.

I'll be glad to help, the mod takes only a few minutes if you know what components to change, but I'm afraid it will be way too overkill to send the board to Spain and back to USA just to change a few passives.

I'm pretty sure you can find some local experienced technician that, after viewing the document, can perform the mod quickly and for little money. I'll be glad to help him if there is something unclear.

Just a tip on the ACC1 audio: The rig, as it is, will give you a low audio fidelity through this connector, as it is intended for digital-like signals only. On the MAIN UNIT board there is an opamp (IC503b) which works near saturation and also has some high-pass filtering on it. I've changed a few components on my rig to get high-fidelity audio though ACC1 and this required to remove the whole board form the rig and change two or three SMD resistors and capacitors... It's not and easy mod... I suggest you do it only if you're comfortable with this level of hacking.

Anyway, with the mod I described you'll get quite some bandwidth just using the front mic connector. The ACC1 audio is better, yes, but not so noticeable.

By the way, if you transmit on AM, I suggest to increase R426 to at least 4.7kOkm (in order to get similar TX audio gains on AM and SSB) and to reduce R449 to 7.8KOhm or so (to get full 100% AM modulation depth without reaching the opamp positive output rail). Both are on the DSP board. Otherwise, if your rig is as mine, you won't get a decent audio level on your AM transmission.

Hummmm. It appears that the whole server is down.... I don't have access to other stable web server, so anyone needing it, send me an email to daniel_at_z-ha-dum_dot_dyndns_dot_org . Te file is free to share, so if anyone can post it on the web, feel free to do so.

The modifications you have done on your Icom 756 require a lot of skill and knowledge. Unfortunately I myself can't do what you can do. So I'm going to have to buy another radio more set up for ESSB for myself because that last hacking mod on the main board for the acc1 fidelity audio is to complex for me and here in New Zealand not a lot of people are on hand to do what's required.

Thanks for all the info, it will most probably help a lot of other operators that can do these mods to get the voodoo in there audio with the Icom 756..

I don't remember exactly, but it was between 10nF and 100nF. I only used them to block the DC component coming from the radio, otherwise the filter shorts it out to ground. Nothing fancy like impedance matching or so...

You cannot put decent analog audio through ACC without changing a few components on the bottom of the Main Unit board. This requires removing the board from the radio. This is independent of increasing the TX audio bandwidth, you still can use the front mic and go wide...